Field of the Invention
This invention relates to the field of optical technology, and in particular, it relates to light source systems and projection devices using the light sources.
Description of the Related Art
Currently, high brightness color light sources are needed in a wide variety of applications, including stage lighting, projection display and RGB (red, green and blue) backlight, etc. Traditionally, gas discharge lamp (for example, super high pressure mercury lamp) as a high brightness light source has been used in special lighting and display fields. However, mercury can cause environmental pollution, and an environmental friendly light source which can replace the super high pressure mercury lamp is highly desired in the industry.
FIG. 1 is the structure diagram of a current light source technology. As shown in FIG. 1, the light source system comprises an excitation light source 101, an optical lens 102, a color wheel 103 and a driving device 104. The excitation light source 101 is used to generate an excitation light 106. The optical lens 102 converges the excitation light 106 and relays it to the color wheel 103. The color wheel 103 has different segments with different phosphors coated on them respectively. When the color wheel 103 rotates around the rotation axis 105 under the driving of the driving device 104, a color light sequence is generated from phosphor coatings excited by the excitation light 106 successively. For example, the phosphor coatings may include red phosphor, green phosphor and yellow phosphor. So when the red phosphor segment in the color wheel 103 is in the propagation path of the excitation light, high brightness red light is generated by the red phosphors that is under the excitation of the excitation light 106. The generation process of the green light and yellow light are the same as the red light.
However, among all the current phosphor coatings, the conversion efficiency of the red phosphor is much lower than the other color phosphor. So there need be an additional light source to improve the red color light.
FIG. 2 is the structure diagram of another current light source technology. As shown in FIG. 2, the light source system comprises an excitation light source 201, a supplemental light source 202, a light conversion device 203 generating a red light, and a dichroic filter 204. The red light 207 generated by the supplemental light source 202 and the excitation light 205 generated by the excitation light source 201 (e.g. blue color light) are combined by the dichroic filter 204, and then the red light 207 is incident to and transmitted by the light conversion device 203 while the excitation light 205 is used to excite the light conversion device 203 to generate red converted light 206. So the red converted light 206 is supplemented by the red light 207. Unfortunately, the light conversion device 203 has high reflectivity for red light, which is usually about 50%, so the red light 207 reflected by the light conversion device 203 will propagate along the incoming path back to the supplemental light source 202, which result in a reduction of optical efficiency. Moreover, for the red converted light 206 generated by the light conversion device 203, only a part of it can propagate forward, and the rest will propagate backward toward the dichroic filter 204 and ultimately reaches the excitation light source 201 or reflected to the supplemental light source 202. This also causes a low optical efficiency.
In conclusion, a light source system and a projection device are desired that can solve the above technology problems generally existing in current light source system.